Acetabular fractures: optimal imaging

Posterior Wall Fragments in Acetabular Both-Column Fractures: Morphology, Type, and the Significance of its Projection

OBJECTIVE

Most both-column acetabular fractures are combined with posterior wall fragments. However, the morphology of this posterior wall is varied, and how to fix this posterior wall remains a controversial topic. To investigate the morphological characteristics of posterior wall fragments of both-column acetabular fractures and select corresponding fixation methods.

METHODS

Data from 352 patients with acetabular fractures admitted to the level one trauma centre in our hospital between January 2006 and December 2022 were collected. The morphology of posterior wall fragments was observed and analyzed in 83 cases of both-column acetabular fractures and classified according to the consistency of posterior wall morphology. A fracture map of the posterior wall was created on a normal template according to the three morphological types of posterior wall fragments. Finally, the high-incidence area of the posterior wall fracture was projected onto the iliac fossa and the medial side of the posterior column to guide the fixation of the posterior wall fragment using the anterior intrapelvic approach.

RESULTS

Fractures were divided into four types: I, large posterior wall fragment which was high in the ilium bone (34 cases, 41.0%); II, posterior wall fragment in the acetabular parietal region (18 cases, 21.7%); III, posterior wall marginal fracture (10 cases, 12.0%); and IV, non-combined posterior wall fracture (21 cases, 25.3%). The most common morphologies of the posterior wall fragments of the first two types were mapped and projected onto the anterior iliac inner plate and medial side of the posterior column, where the corresponding area could be used to guide the insertion of the internal fixation.

CONCLUSION

Both-column acetabular fractures combined with posterior wall fractures can be divided into four types according to the morphology of the posterior wall fragment. Understanding the corresponding three-dimensional morphology and projection position of different types of these fragments can help surgeons determine the position and orientation of internal fixation of posterior wall fractures.

Trans-sacral screw fixation of posterior pelvic ring injuries: review and expert opinion

Posterior pelvic ring injuries (i.e., sacro-iliac joint dislocations, fracture-dislocations, sacral fractures, pelvic non-unions/malunions) are challenging injury patterns which require a significant level of surgical training and technical expertise. The modality of surgical management depends on the specific injury patterns, including the specific bony fracture pattern, ilio-sacral joint involvement, and the soft tissue injury pattern. The workhorse for posterior pelvic ring stabilization has been cannulated iliosacral screws, however, trans-sacral screws may impart increased fixation strength. Depending on injury pattern and sacral anatomy, trans-sacral screws can potentially be more beneficial than iliosacral screws. In this article, the authors will briefly review pelvic mechanics and discuss their rationale for ilio-sacral and/or trans-sacral screw fixation.

Mapping of both column acetabular fractures with three-dimensional computed tomography and implications on surgical management

Background

The primary goal of this study was to create a frequency map of a series of surgically treated both-column fractures and to explore its implications on surgical management.

Methods

We used a consecutive series of 71 both-column fractures to create 3-dimensional reconstruction images, which were superimposed and oriented to fit a model hemipelvis template by aligning specific pelvis landmarks. Fracture lines were identified and traced to create a fracture map of both-column fractures. Then the possible clinical implications of fracture line map were explored.

Results

Fracture location is closely related to the distribution of fracture line. Of 71 fractures that met the criteria for inclusion, we found the most common pattern demonstrated by coexisting fracture lines. The anterior column was involved by 66% of the fractures extending obliquely from the anterior superior spine to the ischial spine, while 62% of the fractures involved the anterior column extending approximately vertically from the iliac crest to the acetabular roof. Additionally, 39% of the fractures involved the posterior column traversing posterior wall. Furthermore, the high fracture line intensity (n = 65, 92%) formed a Y-shaped pattern, which highlighted the consistency of the patterns.

Conclusions

Surgically treated both-column fractures display very common patterns. The most common pattern is the low anterior column fracture in nearly two thirds of cases, the high anterior column fracture in three fifths of cases and the posterior column fracture with posterior wall involvement in nearly two fifths of cases. These study results may help surgeons to yield insight relevant to surgical approaches, reduction, fixation strategies and even implant design for both-column fractures.

Imaging Evaluation of Pediatric Extremity Trauma, Part I: Injury Patterns in the Immature Skeleton and Imaging Modalities

The injury patterns encountered in the extremities of infants and children differ from those seen in adults, predominantly due to significant differences in the composition and structure of the immature skeleton. A variety of fractures occur that are unique to children, and some of them tend to be subtle and easily overlooked. Plain radiographs remain an essential tool for the detection and management of such injuries. In addition, a variety of imaging modalities are available (e.g., CT, MRI, ultrasound) that provide additional information about musculoskeletal injuries which can be helpful in selected cases. This article presents the different types of injuries that can be expected in pediatric extremity trauma and discusses methods to improve detection on plain radiographs. The relative value and indications of other imaging modalities are also discussed.

CT-generated radiographs in patients with pelvic ring injury: can they be used in lieu of plain radiographs?

Background

Pelvic ring injury classification traditionally is made using plain radiographs. Recent studies suggest that computed tomography (CT)-generated images have higher diagnostic accuracy than plain films for the classification of acetabular fractures. However, similar studies have not been performed for pelvic ring injuries. The purpose of this study was to compare CT-generated and plain radiographs in terms of the ability of surgeons at different experience levels to identify pelvic injury type.

Methods

CT-generated and plain radiograph image sets were created from 15 pelvic ring injury patients with known classification morphology. Three groups, each consisting of three orthopaedic surgeons representing different levels of expertise, viewed these image sets and recorded their diagnoses. These diagnoses were compared to the gold standard findings of the treating physician and to each other.

Results

Overall, there was a significantly improved ability to correctly classify pelvic ring injury type by CT-generated radiographs as compared to plain radiographs (p < 0.01). However, analysis of the groups revealed that this difference was limited to the less experienced groups (p < 0.05).

Conclusions

CT-generated radiographs are diagnostically beneficial for less experienced surgeons and at least as good as conventional plain radiographs for experienced surgeons in classifying pelvic ring injuries. Therefore, CT-generated radiographs may be clinically valuable: sparing the patient additional radiation exposure and discomfort by avoiding the reordering of plain radiographs when the initial studies are of poor quality, as well as serving as a possible alternative for supplemental initial injury plain radiographic views.

Acetabular fractures: what radiologists should know and how 3D CT can aid classification

Correct recognition, description, and classification of acetabular fractures is essential for efficient patient triage and treatment. Acetabular fractures may result from high-energy trauma or low-energy trauma in the elderly. The most widely used acetabular fracture classification system among radiologists and orthopedic surgeons is the system of Judet and Letournel, which includes five elementary (or elemental) and five associated fractures. The elementary fractures are anterior wall, posterior wall, anterior column, posterior column, and transverse. The associated fractures are all combinations or partial combinations of the elementary fractures and include transverse with posterior wall, T-shaped, associated both column, anterior column or wall with posterior hemitransverse, and posterior column with posterior wall. The most unique fracture is the associated both column fracture, which completely dissociates the acetabular articular surface from the sciatic buttress. Accurate categorization of acetabular fractures is challenging because of the complex three-dimensional (3D) anatomy of the pelvis, the rarity of certain acetabular fracture variants, and confusing nomenclature. Comparing a 3D image of the fractured acetabulum with a standard diagram containing the 10 Judet and Letournel categories of acetabular fracture and using a flowchart algorithm are effective ways of arriving at the correct fracture classification. Online supplemental material is available for this article.

Easily Missed Fractures in the Lower Extremity

As long as radiography remains cheap and provides value in patient care, it will continue to be widely used as a front-line imaging technique. There are limitations to what a radiograph can depict, however. It is imperative to understand the limitations of radiography to avoid pitfalls owing to the overlap of numerous osseous structures. This article reminds the reader of the association between certain radiographic abnormalities and the anatomic relevance in the patient. Although interpretive errors occur in fast-paced, high-volume emergency settings, meticulous attention to changes in the cortex and medullary bone may help to keep errors to a minimum.

CT-generated radiographs in obese patients with acetabular fractures: can they be used in lieu of plain radiographs?

BACKGROUND

Acetabular fracture diagnosis is traditionally made with AP and oblique pelvic plain radiographs. Obesity may impair diagnostic accuracy of plain radiographs. New CT reconstruction algorithms allow for simulated radiographs that may eliminate the adverse imaging effects of obesity.

QUESTIONS/PURPOSES

In obese patients with acetabular fractures, we compared CT-generated and plain radiographs in terms of (1) ability to classify fracture type, (2) agreement in fracture classification, and (3) surgeon performance at different experience levels.

METHODS

CT-generated and plain radiograph image sets were created for 16 obese (BMI>35) patients with 17 acetabular fractures presenting from 2009 to 2011. Three orthopaedic trauma attending physicians, three senior residents, and three junior residents independently viewed these sets and recorded their diagnoses. These diagnoses were compared to the postoperative findings, which we defined as the gold standard for diagnosis. To assess intraobserver reliability, the same observers reviewed a rerandomized set 1 month later. We had 80% power to detect a 25% difference in the percentage of correctly classified fractures based on a post hoc sample size calculation and 80% power to detect a 0.10 difference in κ value based on both a priori and post hoc sample size calculations.

RESULTS

With the numbers available (153 observations in each image set, 51 for each of the three observer groups), we found no differences between CT-generated and plain radiographs, respectively, in terms of percentage of correct diagnoses for the observer groups (all observers: 54% versus 49%, p=0.48; attendings: 61% versus 59%, p=0.83; senior residents: 51% versus 53%, p=0.84; and junior residents: 49% versus 35%, p=0.16). Furthermore, agreement between CT-generated and plain radiographic fracture classifications was substantial (κ=0.67). Nonetheless, the attending and senior resident groups performed better in correctly classifying the fracture than the junior residents when using plain radiographs (p=0.01 and p=0.049, respectively). Performance was not different when comparing the attendings to the senior resident and junior groups or comparing the senior residents to the junior residents using CT-generated radiographs (p=0.32, p=0.22, and p=0.83, respectively).

CONCLUSIONS

CT-generated radiographs are as good as plain radiographs for experienced surgeons for classifying acetabular fractures in obese patients. CT-generated imaging may be valuable in both teaching and clinical settings, and it may spare the patient additional radiation exposure and discomfort.

LEVEL OF EVIDENCE

Level II, diagnostic study. See the Instructions for Authors for a complete description of levels of evidence.

The role of computed tomography in musculoskeletal trauma

Computed tomography is the undisputed gold standard in the imaging of acute trauma, despite the introduction of focused assessment with sonography for trauma and magnetic resonance imaging. However, the role of computed tomography is far wider than just polytrauma imaging: its high spatial resolution, short scan times and very high sensitivity and specificities make computed tomography useful in the diagnosis of subtle injuries, as well as providing a general overview of other compartmental injuries. Three-dimensional reconstructions illustrates complex injury patterns clearly, aiding surgical planning and permitting accurate orthopaedic hardware follow-up. This article outlines some of the basic properties of computed tomography using examples from musculoskeletal trauma, to illustrate to clinicians what computed tomography can and cannot do for their practice.

The use of intraoperative three-dimensional imaging (ISO-C-3D) in fixation of intraarticular fractures

INTRODUCTION

The purpose of this study was to analyse the applicability and advantages of the intraoperative use of a mobile isocentric C-arm with three-dimensional imaging (Siremobil ISO-C-3D) in fixation of intraarticular fractures.

METHODS

After the fixation was judged to be satisfactory relying on the images provided by routine fluoroscopy, intraoperative CT visualisation with ISO-C-3D was performed to evaluate the fracture reduction and implant position. Intraoperative revision was performed based on the additional information ISO-C-3D provided beyond routine fluoroscopy. ISO-C-3D was used on a series of 72 closed-intraarticular fractures in 70 patients. Fracture distribution was: calcaneus (25), tibial plateau (17), tibial plafond (12), acetabulum (11), distal radius (3), ankle Weber-C (3) and femoral head (l). The primary outcome measure was revision rate after final ISO-C-3D data acquisition and prior to wound closure. Secondary objectives were to measure the additional time required for ISO-C-3D use and to determine the rate of further re-do surgeries.

RESULTS

Eight out of 72 (11%) fracture fixations were judged by the surgeon to require intraoperative revision following ISO-C-3D imaging. Prior to leaving the operating room, the surgeon was satisfied with fracture alignment in all the procedures. The mean additional operative time using ISO-C-3D was 7.5 min (8.2% of the mean total operative time). No patient required re-do surgery.

CONCLUSION

: Intraoperative three-dimensional visualisation of intraarticular fractures enables the surgeon to identify inadvertent malreductions or implant malpositions which may be overlooked by routine C-arm fluoroscopy and hence may eliminate the need for re-do procedures. ISO-C-3D adds little operative time and may preclude the need for pre-operative and post-operative CT-scans in selected cases.

Interobserver agreement for Letournel acetabular fracture classification with multidetector CT: are standard Judet radiographs necessary?

PURPOSE

To retrospectively evaluate interobserver agreement for Letournel acetabular fracture classification with radiography alone and multidetector computed tomography (CT) alone and to retrospectively assess whether standard Judet views lead to a change in the classification.

MATERIALS AND METHODS

Institutional review board approval was obtained; informed consent was not required for this HIPAA-compliant study, which included 101 imaging studies performed in 99 patients (78 male, 21 female; mean age, 43 years; age range, 15-86 years) with acetabular fractures. Two musculoskeletal radiologists independently classified the fractures with radiography alone and multidetector CT alone. Multiplanar reformatted and three-dimensional (3D) CT images were reviewed at a computer workstation. Readers were shown radiographs at the end of multidetector CT image reading to see if this would change the multidetector CT-based classification. kappa Values were calculated to assess interobserver agreement. For surgically treated patients, the McNemar test was used to compare the accuracy of readers' classifications. The reference standard was a combination of preoperative radiographic and multidetector CT image findings and intraoperative findings.

RESULTS

Interobserver agreement was moderate (kappa = 0.42) with radiography and substantial (kappa = 0.70) with multidetector CT. Multidetector CT classification was changed in two cases (one case for each reader) after standard Judet views were added. In 73 surgically treated patients, agreement with the surgeons' classification was higher with multidetector CT than with radiography (P < .01 for one reader, P = .06 for the other reader).

CONCLUSION

There is substantial interobserver agreement for Letournel acetabular fracture classification with multiplanar reformatted and 3D multidetector CT images. Standard Judet pelvic radiographs add little information for changing the multidetector CT classification.

Advances in musculoskeletal radiology: multidetector computed tomography

The clinical potential of multidetector CT is significantly increased because of the possibility of almost instantaneous isotropic reformations in all planes, increased speed and coverage, and easy interpretation. Multidetector CT has a significant role in the correct and quick diagnosis and treatment of emergency department patients. In complex anatomic regions, it is an important diagnostic aid, and it allows exact classification of the bony lesion, which is important for diagnosis, treatment, and prognosis. Multidetector CT visualizes congenital deformities and is useful in oncology. Ongoing developments comprise diagnosis and treatment, preoperative and postoperative planning, and hard-ware imaging. Relatively new but well-known applications of multidetector CT include intraoperative navigation, implant and prosthesis planning and surgery simulation, vertebroplasty, and pedicle screw installations.

Distinction of Long Bone Stress Fractures from Pathologic Fractures on Cross-Sectional Imaging: How Successful Are We?

OBJECTIVE

The objectives of our study were to define CT and MRI features that distinguish pathologic fractures from stress fractures and to compare the performance of CT and MRI with radiography.

MATERIALS AND METHODS

Two reviewers retrospectively reviewed 45 MR images, 37 CT scans, and 43 radiographs in 59 patients (30 biopsy-proven pathologic fractures and 29 stress fractures followed to resolution). The features observed on MRI were abnormal bone marrow (well-defined, ill-defined); intracortical, periosteal, or muscle T1 or T2 signal; endosteal scalloping; and a soft-tissue mass. The features seen on CT were marrow abnormality and character (well-defined, ill-defined, permeative, moth-eaten), endosteal scalloping, periosteal reaction (benign, aggressive), and a soft-tissue mass. Reviewers rated their confidence for diagnosing a pathologic fracture on a 1-3 scale (< 50%, 50-95%, > 95% sure, respectively) with each technique. Performance of each technique was defined by reviewer accuracy and area under the receiver operating characteristic curve (Az); the frequency with which the MRI and CT features were associated with pathologic and stress fractures was calculated.

RESULTS

For both reviewers, accuracy for differentiating pathologic from stress fractures was highest on MRI (accuracy/Az: reviewer 1, 98%/0.97; reviewer 2, 93%/0.99); CT (reviewer 1, 88%/0.83; reviewer 2, 82%/0.90) was less accurate than radiography (reviewer 1, 94%/0.98; reviewer 2, 88%/0.96). On MRI, pathologic fractures compared with stress fractures exhibited well-defined T1 marrow signal (83% vs 7%, respectively; p < 0.001), endosteal scalloping (58% vs 0%, p < 0.001), muscle signal (83% vs 48%, p = 0.026), and a soft-tissue mass (67% vs 0%, p < 0.001). On CT, pathologic fractures compared with stress fractures exhibited marrow abnormality (84% vs 17%, respectively; p = 0.001), endosteal scalloping (44% vs 0%, p = 0.006), and aggressive periosteal reaction (36% vs 0%, p = 0.04).

CONCLUSION

MRI is useful for distinguishing pathologic from stress fractures, especially after inconclusive radiographic findings. Specifically, pathologic fractures exhibit well-defined T1 marrow alterations, endosteal scalloping, and adjacent soft-tissue abnormalities.

Distinguishing stress fractures from pathologic fractures: a multimodality approach

Whereas stress fractures occur in normal or metabolically weakened bones, pathologic fractures occur at the site of a bone tumor. Unfortunately, stress fractures may share imaging features with pathologic fractures on plain radiography, and therefore other modalities are commonly utilized to distinguish these entities. Additional cross-sectional imaging with CT or MRI as well as scintigraphy and PET scanning is often performed for further evaluation. For the detailed assessment of a fracture site, CT offers a high-resolution view of the bone cortex and periosteum which aids the diagnosis of a pathologic fracture. The character of underlying bone marrow patterns of destruction can also be ascertained along with evidence of a soft tissue mass. MRI, however, is a more sensitive technique for the detection of underlying bone marrow lesions at a fracture site. In addition, the surrounding soft tissues, including possible involvement of adjacent muscle, can be well evaluated with MRI. While bone scintigraphy and FDG-PET are not specific, they offer a whole-body screen for metastases in the case of a suspected malignant pathologic fracture. In this review, we present select examples of fractures that underscore imaging features that help distinguish stress fractures from pathologic fractures, since accurate differentiation of these entities is paramount.

CT with 3D rendering of the tendons of the foot and ankle: technique, normal anatomy, and disease

Three-dimensional rendering of computed tomographic data with volume rendering (VR), shaded surface display (SSD), and maximum intensity projection has been performed for over 20 years. In the foot and ankle, no one image reformatting technique is satisfactory for displaying every anatomic relationship or disease process. Two-dimensional multiplanar reformatted (MPR) images are the basic images used for diagnosis. MPR images are especially useful for identifying small fractures. VR is useful for demonstrating the relationships between ankle tendons and the underlying osseous structures, and SSD is useful when fractures extend to the articular cortex and a disarticulated view is desired. Three-dimensional images are helpful in patients with congenital deformities, arthritis, and trauma.

Acetabular Fractures Revisited:Part 2, A New CT-Based Classification

OBJECTIVE

The objective of this investigation was to provide a new CT-based classification of acetabular fractures.

MATERIALS AND METHODS

The axial CT scans of 112 randomly selected acetabular fractures in patients admitted to a level 1 trauma center between January 1998 and December 2000 were analyzed by an experienced orthopedic trauma surgeon and two experienced emergency radiologists. When available, 3D reformatted images were analyzed as well. The fracture pattern for each acetabular fracture, with respect to column walls and extension beyond the acetabulum, when present, was recorded. Fracture comminution was not a defining characteristic.

RESULTS

Analysis of the 112 acetabular fracture patterns showed that each fracture fell into one of four broad categories. Category 0 included wall fractures only. Category I included acetabular fractures limited to a single (anterior or posterior) column. Category II fractures included those involving both the anterior and posterior columns; category II fractures were further subdivided into those with no fracture extension beyond the acetabulum, those with superior or inferior extension, and those with both superior and inferior extensions beyond the acetabulum. Category III fractures included only the "floating" acetabulum, which is defined as an acetabular fracture in which the acetabulum is separated from the axial skeleton both anteriorly and posteriorly.

CONCLUSION

The axial CT display of acetabular fracture patterns provides a basis for a classification of acetabular fractures that is simple, unambiguous, readily understood by both radiologists and orthopedic surgeons and provides clear direction for both diagnosis and surgical treatment planning. Category and subcategory fracture specificity creates a mechanism for intra- and interdepartmental postoperative assessment of any of the individual acetabular fracture types.

Accuracy and Time Efficiency for the Detection of Thoracic Cage Fractures

OBJECTIVE

To compare the accuracy and time efficiency of volume rendering (VR) compared with transverse images of multidetector-row computed tomography data to identify thoracic cage fractures.

METHODS

Computed tomography scans of 50 patients with acute blunt chest trauma were retrospectively analyzed by using VR and transverse images. The number, location, and type of rib and sternal fractures revealed by these viewing methods were compared, and the time needed for diagnosis was measured.

RESULTS

Thirty of 50 patients had a total of 178 rib fractures. The mean sensitivity, specificity, and accuracy for their detection were similar for transverse (96%, 100%, and 99%) and VR (98%, 100%, and 100%) images. Three sternal fractures were correctly diagnosed with VR, and 1 was missed on transverse images by both readers. The time to read VR images (mean of 105 seconds) was significantly reduced compared with the time needed for transverse image reading (mean of 167 seconds; P < 0.001).

CONCLUSION

Volume rendering of computed tomography data depicts thoracic cage fractures with a high accuracy similar to that of transverse images but is considerably faster.

Stereoscopic 3D CT vs standard 3D CT in the classification of acetabular fractures: an experimental study

The accuracy of stereoscopic and standard three-dimensional (3D) CT in the classification of acetabular fractures was compared. A receiver operating characteristic (ROC) analysis was performed by two radiologists and two surgeons blinded to the presence of acetabular fractures in an animal model (a total of 62 porcine hips, 40 with artificial acetabular fractures). Classification of acetabular fractures was adopted from the literature. Interpretation was performed on a workstation using two specific volume rendering algorithms; unshaded and shaded bone. The ROC analysis did not demonstrate any benefit in stereoscopic 3D CT compared with standard 3D CT.

3D CT versus axial helical CT versus conventional tomography in the classification of acetabular fractures: a ROC analysis

AIM

To assess the diagnostic power of three-dimensional computed tomography (3D CT), axial helical computed tomography (CT) and conventional tomography in the classification of acetabular fractures by interdisciplinary review.

MATERIALS AND METHODS

Receiver operating characteristics (ROCs) were assessed for two radiologists and two surgeons blinded to the presence of acetabular fractures in an animal model (a total of 62 porcine hips, 40 of them with artificial acetabular fractures). Main target parameter was the diagnostic accuracy in the classification of the artificial fractures following Judet et al.

RESULTS

ROC analysis for radiologists showed A(z) values of 0.83 for 3D CT, 0.81 for axial helical CT, and 0.78 for conventional tomography; differences between the three techniques were not significant (P = 0.46-0.73). A(z) values for the surgeons were 0.87 for 3D CT, 0.68 for axial helical CT, and 0.60 for conventional tomography; 3D CT was significantly better than axial helical CT (P = 0.01) and conventional tomography (P = 0.001). The differences between axial helical CT and conventional tomography were not significant (P = 0.37).

CONCLUSION

Acetabular fractures are best classified by 3D CT, followed by axial helical CT and conventional tomography when assessed by surgeons. 3D CT did not provide any additional significant benefit in the classification performed by radiologists.

Volume-rendered three-dimensional spiral CT: musculoskeletal applications

Spiral computed tomography (CT) is a powerful modality for evaluation of the musculoskeletal system, particularly when coupled with real-time, volume-rendering reconstruction techniques. Including volume-rendered spiral CT in routine musculoskeletal imaging protocols can change management in a significant number of cases. In cases of trauma, subtle fractures--particularly those oriented in the axial plane--are better seen on volume-rendered images. Complex injuries can be better demonstrated with volume-rendered images, and complicated spatial information about the relative positions of fracture fragments can be easily demonstrated to the orthopedic surgeons. The use of intravenously administered contrast material allows simultaneous evaluation of osseous and vascular structures within the affected area. Evaluation of suspected infectious or neoplastic disease is also aided by including volume-rendered imaging in the musculoskeletal spiral CT examination. The extent of disease can be thoroughly evaluated with volume-rendered images, and therapeutic planning--be it surgical or medical--is aided by the anatomic information available from volume-rendered images. Postoperative studies in patients with orthopedic hardware also benefit from volume-rendered imaging. Volume rendering eliminates most streak artifact and produces high-quality images on which the relationships among hardware, bones, and bone fragments are well demonstrated.

Tomography versus computed tomography for assessing step off in intraarticular distal radial fractures

Computed tomography scans have supplanted conventional tomography for many applications and often are considered the imaging study of choice for assessing intraarticular distal radial fractures. Concern about cost containment in healthcare delivery prompts the question of whether the two studies provide comparable information and at what cost. Common intraarticular distal radial fractures were created in 12 lightly embalmed cadaveric specimens. The fractures were fixed with radiolucent Kirschner wires. Articular step off was measured with a caliper. Plain radiographs, computed tomography scans, and trispiral tomograms were obtained of each specimen. Maximal step off was measured blindly by two musculoskeletal radiologists and four hand surgeons. The radiographic measurements were compared with the actual step off and expressed as a positive or negative deviation from the actual value. There was no statistically significant difference between computed tomography scans and tomograms in predicting step off. In addition, the difference between actual and radiographic measurements was insignificant in tomogram readings and different in one of the computed tomography measurements. In the authors' institution, a tomogram costs $200, and a computed tomography scan costs $562. Trispiral tomography is more accurate and cost effective than computed tomography, and thus when available should be considered the imaging modality of choice for assessing articular step off in distal radius fractures.

Rotational imaging of complex acetabular fractures

Understanding complex acetabular fractures is difficult and may require three-dimensional reformatted computed tomographic (CT) images. This paper evaluates a technique, digital rotational imaging (DRI), that displays multiple oblique images of the pelvis and acetabulum. When viewed statically, DRI provides optimal iliac and obturator oblique projections, often differing in obliquity from the conventional 45-degree orthogonal views. Dynamic DRI viewing in rapid sequence provides a three-dimensional effect that improves perception of acetabular fracture relationships.

Spiral computed tomography for staghorn calculi

OBJECTIVES

To assess the utility of spiral computed tomography (CT) with three-dimensional reconstruction for preoperative planning of percutaneous nephrostolithotomy in patients with complex branched calculi (full staghorns).

METHODS

Patients with complex branched stones were imaged with spiral CT with three-dimensional reconstruction. These images were compared with standard imaging modalities, including excretory urography and plain radiographs, for planning percutaneous access for nephrostolithotomy. The utility of the scan was evaluated.

RESULTS

Ten patients with branched calculi were studied. Anatomic abnormalities were present in 5 patients. Excellent three-dimensional images were obtained in all patients without any complications related to the study. In 1 patient with multiple calculi in a horseshoe kidney, the three-dimensional image indicated a branched stone. The spiral CT scan was not helpful in directing percutaneous access in any patient. In a single patient, residual fragments noted during nephrostolithotomy were located by reference to the spiral CT scan.

CONCLUSIONS

Spiral CT scans with three-dimensional reconstruction provide three-dimensional imaging of branched renal calculi. This modality provides minimal additional information over that obtained from standard radiographic studies for guiding nephrostolithotomy and cannot be recommended as a routine preoperative study. It was helpful in 1 patient to locate a residual fragment.

Morphologic evaluation and surgical simulation of ossification of the posterior longitudinal ligament using helical computed tomography with three-dimensional and multiplanar reconstruction

STUDY DESIGN

Using helical computed tomography with three-dimensional and multiplanar reconstruction, ossification of the posterior longitudinal ligament in the cervical and thoracic region was observed. Preoperative simulation also was performed, and the availability of these methods was evaluated.

OBJECTIVE

To use preoperative evaluation and simulation with helical computed tomography to enhance the accuracy of excision of ossification of the posterior longitudinal ligament lesion.

SUMMARY OF BACKGROUND DATA

Ossification of the posterior longitudinal ligament lesion is sometimes so complicated that preoperative morphologic evaluation and excision of the lesion are difficult when using only conventional imaging techniques.

METHODS

Seven cases of cervical and two cases of thoracic ossification of the posterior longitudinal ligament were scanned using helical computed tomography at 2-mm or 5-mm slice thickness. Three-dimensional and multiplanar reconstruction were performed at 0.7-mm or 2-mm intervals in the bone window. Surgical simulation of the anterior approach for cervical lesion and posterior approaches for thoracic lesion was performed.

RESULTS

Preoperative direct observation of the ossification of the posterior longitudinal ligament lesion was possible, and the complicated structures could be understood more easily than with other conventional methods. When surgical simulation was performed in the workstation, the ossification of the posterior longitudinal ligament lesion was removed sufficiently on arbitrarily reconstructed view in the spinal canal. When the viewpoint then was changed to the approaching side, the location and dimension of the removed area were determined. In all cases, surgical approach and excision of the ossification of the posterior longitudinal ligament lesion were performed more easily and more precisely than in the surgery with no three-dimensional images.

CONCLUSION

Helical computed tomography with three-dimensional, multiplanar reconstruction would be a valuable tool for evaluation and surgical simulation of ossification of the posterior longitudinal ligament lesion by enhancing the accuracy of the surgical procedure.

Multiplanar display of spiral CT data of the pulmonary hila in patients with lung cancer. Preliminary observations

Spiral or helical computed tomography (CT)-generated multiplanar reconstructions were used in the radiological assessment of the pulmonary hila in patients with central lung cancer. Twelve patients with non-small-cell lung cancer and hilar abnormalities were examined with contrast-enhanced spiral CT. Studies were performed on a Siemens Somatom S or Plus-S scanner using either a 24- or 32-second spiral. The study volume was from the arch of the aorta to the inferior pulmonary veins done in a single breath-hold, using 4-mm collimation, and reconstructed at 2-mm intervals. We assessed the quality of vascular enhancement and of multiplanar reconstructions. Bronchoscopic, surgical, and pathological findings were correlated. Excellent vascular opacification and good-quality reconstructions were obtained in all patients. No interscan motion was detected. No problems were encountered with the breathholding technique or in the reconstruction of images, even in patients with poor respiratory function. Multiplanar reconstructions were useful for the evaluation of mediastinal including vascular and airways invasion, for optimal definition of lymph node groups, for the planning of bronchoscopically guided biopsy, as well as for endobronchoscopic laser coagulation therapy and surgical treatment. Spiral CT-generated multiplanar reconstructions of the hila are helpful for staging, solving problems, guiding bronchoscopy, and planning surgery. Even patients with limited respiratory reserve can successfully complete the examination.

Computed tomography scanning with image reconstruction in evaluation of distal radius fractures

Seventeen patients with 18 intraarticular distal radius fractures underwent computed tomography (CT) scanning and image reconstruction to evaluate their distal radius fractures. All patients were selected prospectively because of intraarticular extension and/or displacement of their fractures on pre- or post reduction plain films. Patients who were not surgical candidates for open reduction and internal fixation of their fracture were not included in the study. X-ray films and CT scans were viewed separately and in random order by a senior radiologist not familiar with the cases. Both x-ray films and CT scans readily showed extension of fracture lines into the radiocarpal joint, radial shaft, and the ulnar styloid, but CT scans were better than x-ray films at demonstrating fracture involvement of the distal radioulnar joint, the extent of articular surface depression, and the amount of comminution. Due to the cost, it is recommended that the test only be used for patients who are surgical candidates for open reduction and internal fixation or when more information about the extent of comminution and joint depression is required.

Three-dimensional computed tomography cholangiography: a new technique for biliary tract imaging

Knowledge of the segmental anatomy and intersegmental biliary connections is an essential prerequisite to the effective management of patients with complex biliary strictures. Three dimensional (3D) imaging has the ability to demonstrate complex anatomical relationships that are difficult to appreciate on simple non-invasive two dimensional (2D) imaging. Our aim was to develop a technique for accurate, non-invasive 3D computed tomography (CT) cholangiography. Contiguous 4 mm CT sections were obtained through the liver during a dynamic bolus of 200 ml IV contrast. 3D surface reconstructions were then performed, the biliary system was isolated from surrounding hepatic parenchyma using segmentation and contrast threshold algorithms. 14 patients (six females, eight males, median age 68 years (range 48-82)) were studied. 13/14 had malignant biliary obstruction and one had obstruction secondary to a pancreatic pseudocyst. Obstruction was at the liver hilum in eight, the common bile duct in five and the common hepatic duct in one. Four patients had biliary endoprostheses but were symptomatic from inadequate drainage. There was good demonstration of the biliary anatomy, obstructed segments and intersegmental biliary connections in 13/14; irregular biliary dilatation secondary to primary sclerosing cholangitis rendered interpretation difficult in one. 3D cholangiography provided a useful adjunct to other imaging techniques. In particular, in patients with complex hilar strictures it aided implementation of appropriate interventional drainage procedures.

Spiral CT of musculoskeletal pathology: preliminary observations

Spiral or helical computed tomography (CT) allows the rapid acquisition of volumes of CT data in a 24- to 32-s time frame. Rapid data acquisition is accompanied by the ability to reconstruct the images at any pre-determined interval (1-10 mm). This technique is optimal for studies requiring iodinated vascular contrast because it allows data acquisition during the peak contrast levels, optimizing lesion detection. The technique is also excellent for studies that need two- and/or three-dimensional reconstruction as it decreases the chance of interscan motion. Spiral CT has significant potential for a wide range of musculoskeletal imaging applications including in musculoskeletal infection, soft tissue tumors, trauma, and in the oncologic patient.

The role of 3D CT in the assessment of acetabular fractures

A total of 16 patients with acetabular fractures were evaluated by plain radiography, axial computed tomography (CT) and three dimensional (3D) CT. It was possible to classify the fracture type in each case from the plain radiographs alone. Axial CT gave additional detail in certain areas, notably the region of the teardrop, the obturator foramen and the acetabular roof. Intra-articular and impacted roof fragments and associated soft tissue injuries were also shown. 3D CT provided the best and most easily interpreted overall assessment of the fractures. In addition to projections equivalent to the plain radiographs, two other views were of particular clinical value in demonstrating surgically inaccessible areas, namely the view of the pelvis from above and the view of the inner aspect of the fractured hemipelvis. However, fracture lines demonstrated on plain radiographs and axial CT were not always apparent on the 3D CT scans. Although 3D CT is a valuable addition to the imaging of acetabular fractures, it is not a substitute for good quality plain radiography and analysis of the axial CT images.

Three-dimensional computed tomography in the assessment of fractures of the acetabulum

Axial CT has, for many years, been shown to be superior to conventional radiology in the demonstration and assessment of acetabular fractures. The more recent development of complex computer programmes has enabled the production of three-dimensional images (3D CT) from sets of contiguous axial scans. 3D CT permits full imaging of the pelvis with the minimum of distress to the patient and with the minimum of radiation exposure. The ability to rotate the 3D images around a variety of axes provides a valuable perceptual link between conventional radiographs and axial CT, and enables the creation of unique images that offer perspectives unobtainable by conventional radiology. The improved visualization of the pelvis leads to more accurate diagnosis of the fracture, and hence better surgical planning and management.

3-dimensional imaging of the pelviocaliceal system by computerized tomographic reconstruction

Safe and efficient performance of percutaneous nephrolithotomy requires 3-dimensional visualization of the pelviocaliceal anatomy. However, currently available modalities offer only 2-dimensional images, from which the operator must mentally reconstruct a 3-dimensional picture of the pelviocaliceal configuration. We evaluated the feasibility of obtaining 3-dimensional images of the pelviocaliceal system with the aid of computerized tomographic reconstruction and present 3 illustrative cases.

A comparison of two approaches to three-dimensional imaging of craniofacial anomalies

Volume-based and surface-based algorithms for three-dimensional rendering of computed tomography (CT) scans of the human skull were compared in patients with craniofacial anomalies. Both methods were applied to a selected sample of 12 clinical CT studies. The number of sections ranged from 24 to 72 and the section thickness from 1.5 to 6.0 mm. Volume renderings were more prone to interpolation artifacts but captured the anatomy in greater detail. The sites of closed cranial sutures, visualized using the volume technique, were not demonstrated using the specific surface rendering technique used in this study. In both techniques the areas of thin bone appeared as gaps.

Real-time, multiplanar computerized tomography: a new diagnostic modality used in the detection and endoscopic removal of a distal ureteral fibroepithelial polyp and adjacent calculus

Ureteral fibroepithelial polyps are rare benign mesodermal tumors that occur predominantly in the upper ureter. We report on a patient with a fibroepithelial polyp in the distal ureter that resulted in entrapment of a calculus and partial obstruction of the collecting system. Preoperatively, diagnosis by standard radiographic methods, such as excretory urogram, retrograde pyelogram and conventional computerized tomography with and without contrast enhancement, was not possible because of the close proximity of the fibroepithelial polyp, the ureteral calculus and calcifications in the adjacent internal iliac artery. The new diagnostic modality of real-time, multiplanar computerized tomography imaging using the Sun/Pixar computer system and the 2D/3D Orthotool software was used to make the correct preoperative assessment. Subsequently, the patient underwent ureteroscopic resection of the polyp and extraction of the calculus. A year later she was free of symptoms and there was no evidence of regrowth of the polyp. To our knowledge this is the first report to describe the use of real-time, multiplanar computerized tomography imaging as an effective diagnostic modality in the genitourinary tract. In addition, this is the first ureteral fibroepithelial polyp reported in the literature to be associated with a ureteral calculus and to be excised endoscopically with no recurrence on long-term followup.

Enhanced computed tomographic techniques for the evaluation of total hip arthroplasty

Computed tomography (CT) has revolutionized the evaluation of musculoskeletal pathology. Until recently, however, CT of the postoperative orthopaedic patient has been severely limited by its inability to provide useful information in the vicinity of acetabular and femoral implants. Typically the hardware produces extensive artifacts that can markedly degrade the whole image. Methods are now available to reduce the metal artifact. Following hip arthroplasty, these methods have been used to plan for revision arthroplasty and to evaluate the contralateral side for avascular necrosis.

Complex shoulder trauma: three-dimensional CT imaging

Volumetric three-dimensional imaging is a new technique for CT image processing which generates realistic, three-dimensional models of complex musculoskeletal anatomy from routine transaxial CT data. Volumetric three-dimensional imaging is particularly helpful in evaluating complex shoulder trauma, demonstrating significant advantages over plain film radiography. Multipartite fractures involving the shoulder girdle are displayed in a comprehensive fashion with 3D imaging. With volumetric imaging as implemented on a Pixar Imaging Computer, a 3D model of the injured shoulder can be generated with overlapping structures removed from view, and then rotated about the vertical and horizontal axis for better understanding of abnormal anatomy prior to surgical correction.